1. Field of the Invention
This invention relates to a sampling device to extract gas for various analyses from a source of gas with a high dust content.
2. Description of the Prior Art
In various combustion furnaces and boilers, such as incinerators to burn sewage sludge and the like, pyrolysis furnaces, coal or oil burning boilers of thermal power plants, and other furnaces, it has been generally practiced to control the combustion by analyzing the combustion exhaust gas therefrom so as to optimize the combustion based on data obtained by the analysis. The analysis includes measurement and detection of the concentration of combustibles, the oxygen concentration, the concentration of nitrogen oxides, and the concentrations of other components of the exhaust gas. When the combustion exhaust gas contains dust particles or sedimentary components, if such exhaust gas is directly introduced into various analytical apparatuses, the dust particles and the sedimentary components tend to deposit in the anayltical apparatuses, whereby the accuracy of the analysis is reduced and in extreme cases, the analysis becomes impossible due to plugging or clogging with the deposits of dust and the like.
To avoid the aforesaid deposits, gas sampling probes with suitable filters mounted thereon are sometimes used, so as to apply the exhaust gas to the analytical apparatuses only after removing the dust particles therefrom.
However, when the content or concentration of the dust particles or sedimentary components such as tar in the exhaust gas is high, the filter of the probe is apt to be fully plugged in a very short time, so that the probe of the prior art has shortcomings in that the filter must be replaced frequently and that continuous measurement is not possible.
To solve the shortcomings, when the exhaust gas contains a large amount of dust particles or tar components, it has been practiced to wash the exhaust gas with water to capture the dust particles or tar components by the water before analyzing the gas. However, the content in the exhaust gas is sometimes very high, for instance in the cases of coal burning boilers of thermal power plants which currently attract much attention from the standpoint of petroleum saving, incinerators of sewage sludge, pyrolysis furnaces for sewage sludge, and cement burning kilns. More specifically, when the dust content in the exhaust gas is 50 g/Nm.sup.3 or more, the piping for extracting the exhaust gas for analysis is apt to be plugged by dust particles in a short time, so that various inconveniences and shortcomings are caused such as the need mechanical means to remove the dust deposits at uniform time intervals or the need of replacement of the exhaust gas extracting pipings.